1. Field of the Invention
The present invention relates to a sheet stacking apparatus, a sheet feeding apparatus, and an image forming apparatus.
2. Description of the Related Art
A universal cassette supporting sheets of various sizes by the same sheet cassette is conventionally used as a sheet cassette provided in a copying machine, a printer, a facsimile machine and the like. The universal cassette is provided with a regulating member to position a sheet end (see, for example, Japanese Patent Laid-Open No. 2007-197159, US 2009/0295068 A1, or Japanese Patent Laid-Open No. 2008-105856).
Then, the position of a sheet is regulated by moving the regulating member to normal positions of various sizes. However, a state in which the regulating member cannot hold a sheet in its normal position may arise after the regulating member moves from the normal position due to an impact caused by insertion/removal of a cassette or the like so that a malfunction such as poor feeding, skew feeding, or double feeding of a sheet occurs during feeding operation.
According to Japanese Patent Laid-Open No. 2007-197159, when a force is applied to a regulating member, movement of the regulating member is regulated by a first engaging portion or a second engaging portion according to the direction in which the force is applied. However, first and second tooth rows are each arranged stepwise and therefore, the height of a holding portion increases and a sheet cassette increases in size, leading to higher costs.
According to US 2009/0295068 A1, a regulating member is reliably held in the regulating position according to the direction in which a force is applied to the regulating member by providing first and second engaged portions in parallel with the bottom of a cassette body and also providing a first engaging member or a second engaging member in parallel with the regulating member. However, the first engaging member or the second engaging member is provided separately and also an elastic member pressing a lock lever is used and therefore, the number of components increases and assembling properties are poor, leading to higher costs.
According to Japanese Patent Laid-Open No. 2008-105856, a regulating member is brought to a fixed state by one engaging portion of the regulating member and thus, when a force is applied to the regulating member, the regulating member can be held in the regulating position only in one direction. However, in addition to the cassette body and the regulating member, many components such as a holding member and an elastic member are used and therefore, assembling properties are poor, leading to higher costs. In addition, the number of components is large and thus, rattling while the regulating member is fixed increases and position regulation of sheet varies, which could lead to deterioration of print precision.
It is desirable to reduce the size of a sheet cassette by reducing the height of a holding portion and to improve assembling properties by reducing the number of components around a regulating member.